1. Field of the Invention
The present invention relates to a splicing system, which is applicable to a control section for a dancer roll moving speed of a corrugate machine, a printing machine provided with an intermittent feeding device of a continuous sheet, a dancer roll section in a winder, and the like.
2. Description of the Prior Art
A general construction of one example of a splicing system for use in a corrugate machine in the prior art is shown in FIGS. 4 and 5. Principal components of the illustrated apparatus are a raw material sheet feeder section 17, a sheet splicer section 3 and a dancer roll section 1. The raw material sheet feeder 17 is a device, in which a rolled sheet 18 consisting of a raw material sheet is rotatably supported via a shaft by a mill roll stand 15 and the sheet is successively rewound and fed in accordance with a necessary feed rate for manufacturing a corrugated cardboard sheet. The subsequent sheet splicer 3 is a device, in which in the case of order change or in the case where an old sheet 18 has been used up, a continuous sheet is formed by connecting the old sheet 18 to a new sheet 18'. The dancer roll section 1 is a section operable in such manner that since the splicing work is carried out while the feeding of the raw material sheet is kept stopped, a length of raw material sheet spent during that splicing work and to be supplemented later is preliminarily stored in the section so that the corrugated cardboard sheet can be manufactured continuously.
Now description will be made briefly on the method (procedure) for splicing. At first, a tip end of a new sheet 2' paid out of a rolled sheet 18' on a mill roll stand 15, has a double-face adhesive tape 19 applied onto its surface after a cutting treatment, its back surface is sucked and held by a press-adhesion bar 20', and stands by under the condition shown in FIG. 5. On the other hand, with regard to the running old sheet 2, an accelerating roll 4 is decelerated by carrying out speed control of a motor 16, the sheet feeding speed is reduced by a braking action of a press roll 24 which pinches the sheet 2 jointly with the accelerating roll 4, further in a sheet stopper section 21 the sheet 2 is pinched by paired bars to be perfectly stopped, and then the stopped old sheet is spliced with the new sheet 2' via the double-face adhesive tape 19 by means of the press-adhesion bar 20'. The thus spliced sheet is pulled by the pinching rotation of the acceleration roll 4 and the press roll 24, and is fed to the dancer roll section 1. After predetermined acceleration, the acceleration roll 4 feeds the sheet to the dancer roll section 1 at a somewhat faster speed than the rate of ejecting the sheet from the dancer roll section 1 and consuming it at the next step of the process, and thus it functions to supplement the stocked amount of sheet that was consumed during the splicing operation. It is to be noted that in FIGS. 4(a) and 4(b), a motor 23 always continues to rotate at a predetermined speed for moving a pair of bearings 14 for a tension roll 5 connected to chains 13 at one location via a powder clutch 11 and sprockets 12, and thereby a proper tension is applied to the sheet being ejected. In the above-mentioned powder clutch 11 which is one kind of electromagnetic disc clutches, finely crushed dry magnetic particles are filled in the space between clutch elements, and a predetermined torque can be set by regulating a current flowing through the powder. It can operate also as a safety device such that in the event that an excessively large torque has been exerted upon the clutch elements, they would slip relative to each other and absorb the exerted torque.
The splicing system in the prior art is constructed and operates in the above-described manner, hence upon sheet splicing work, in the event that the accelerating roll 4 and the press roll 24 have been momentarily decelerated or stopped, as the sheet speed for ejecting the sheet from the dancer roll section 1 to the next step of the process is a constant speed, the tension roll 5 would be pulled back against the inertia of the dancer roll section 1 and the tension roll 5, and so, abrupt change of the sheet tension would appear in the running sheet as shown in FIG. 3(c). On the contrary, after the sheet splicing work, as the feed speed of the sheet 2 is accelerated by the acceleration of the accelerating roll 4, it is necessary to decelerate the moving speed of the tension roll 5 in the pull-back direction, that is to accelerate the moving speed in the normal direction. However, this system had structural shortcomings that if this deceleration (i.e., acceleration in the normal direction) is slower than the acceleration of the sheet 2, the sheet 2 would slacken, while if the feed speed of the sheet 2 is insufficient, the dancer roll would continuously run in the pull-back direction and would strike against a limit stopper, resulting in break of the sheet 2.
In summary, in the above-described sheet splicing system in the prior art, since the splicing between new and old sheets is carried out in the course when a corrugated cardboard sheet is being manufactured successively, upon the splicing work it is necessary to carry out the work while stopping feed of the sheet for a predetermined period of time. While the section having the function of supplementing the difference between the continuous consumption of the sheet on the demand side and the actually fed length of the sheet on the feed side during the stoppage, is the dancer roll section 1, upon splicing as the feed of the sheet is momentarily braked and stopped, the tension in the running sheet would rise abruptly as shown in FIG. 3(A) relating to the prior art, due to the inertia of the tension roll 5 in the dancer roll section 1. In addition, there were shortcomings that after the splicing, sagging was produced in the sheet or the tension in the sheet became extraordinarily high due to unbalance between the feed speed of the sheet and the moving speed of the tension roll 5. Consequently, the prior art system involved various problems that many troubles such as breaking, deformation and instability of running of the sheet were generated.